Generally, pipe joint devices must firmly joint pipes and need to be easily and simply manipulated by workers on a site. To joint pipes together to provide a pipeline in the related art, pipes having appropriate lengths suitable for being manipulated by workers are arranged along a designed pipeline on a site and are jointed together through a welding process using pipe joints, such as reducers, tees and/or elbows. Furthermore, a valve may be installed in a jointed junction of the pipes when it is necessary to control the flow of fluid passing through the pipeline. Hereinbelow, a conventional technique of jointing a valve to a pipe using flanges will be described with reference to FIG. 11. As shown in the drawing, a flange 130 is welded to each of the pipe 110 and the valve 120, and thereafter, the flange of the pipe is jointed to the flange of the valve using nuts and bolts 150 with a gasket 140 interposed between the two flanges.
The above-mentioned pipe jointing technique is advantageous in that it provides a firmly jointed state of the pipe and valve, but the technique is problematic in that cracks may be formed at the jointed junction to cause leakage of fluid from the junction. Furthermore, when the pipe jointing technique is adapted to a city water supply pipeline, the jointed junctions of the pipeline cannot accommodate displacement of pipes which may occur due to the extension and contraction of the pipes caused by temperature variation owing to climate change, or due to the application of impact to the pipes owing to, for example, an earthquake. Such displacement of the pipes may cause breakage of the pipeline, resulting in leakage and contamination of city water. Furthermore, the conventional pipe jointing technique may cause a gas explosion due to gas leakage when the technique is adapted to a gas pipeline, or may cause a safety accident and the loss of lives when the technique is adapted to a pipeline in a nuclear power plant.
In addition to the above-mentioned pipe jointing technique, another jointing technique using clamps and rubber packings has been widely used. However, this jointing technique is problematic in that jointed pipes may be removed from rubber packings when horizontal or vertical force is applied to the jointed pipes. In an effort to overcome the above-mentioned problem, a packing having an improved structure was proposed, which is provided with a ring-shaped channel along an inner surface thereof as shown in FIG. 12. FIG. 13 shows pipes 110 jointed together using both the above-mentioned packing 160 and a clamp 170. When horizontal force is applied to the jointed pipes to make the interval between the pipes wider, the packing 160 is elastically deformed to widen its channel A, thus maintaining its close contact state relative to the pipes 110. When the horizontal force is removed from the pipes, the packing 160 elastically restores its original shape and returns the pipes to their original positions. The above-mentioned packing having the improved structure is advantageous in that the packing effectively maintains the sealed state of the jointed pipes regardless of an application of external force to the pipes and elastically returns the pipes to their original positions. However, the packing is problematic in that impurities may be deposited in the channel of the packing which could reduce the fluid transmission capacity of a pipeline and cause propagation of bacteria in the channel. Furthermore, the above-mentioned packing is specifically shaped to provide the channel as described above, so that the packing may fail to resist fluid pressure.